[Barrelfish-users] [ARM] exception stacks should be 8 bytes aligned

[Kornilios Kourtis]

Hi,

On Thu, May 30, 2013 at 06:25:19PM +0800, Wang Nan wrote:
> Hi,
> 
> Here I propose a small patch which adjust arm exception stacks.
> 
> You can try 'printf("0x%016llx", 0x12345678ULL)' in undef handler. ARM
> abi require stack be 8 bytes aligned, but original code setups 4 bytes
> gaps between 2 stacks, makes irq_stack and undef_stack misaligned.
> 
> reference:
> http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.faqs/ka4127.html

Makes sense to me. Thanks for the patch! I've applied it and will be on
our next release.

cheers,
Kornilios.

> >From 9bc121e69f6846f9eb9db1d03f361d23577213af Mon Sep 17 00:00:00 2001
> From: Wang Nan <wangnan0 at huawei.com>
> Date: Wed, 29 May 2013 20:01:07 +0800
> Subject: [PATCH 1/2] align exception stack with 8 bytes
> 
> ---
>  kernel/arch/armv7/exceptions.S    |   10 +++++-----
>  kernel/arch/hi1380/startup_arch.c |    4 +---
>  2 files changed, 6 insertions(+), 8 deletions(-)



> 
> diff --git a/kernel/arch/armv7/exceptions.S b/kernel/arch/armv7/exceptions.S
> index 427b8b1..fa75dad 100644
> --- a/kernel/arch/armv7/exceptions.S
> +++ b/kernel/arch/armv7/exceptions.S
> @@ -40,27 +40,27 @@
>  abt_stack:
>          .space EXCEPTION_MODE_STACK_BYTES, 0
>  abt_stack_top:
> -        .space 4, 0
> +        .space 8, 0
> 
>  irq_stack:
>          .space EXCEPTION_MODE_STACK_BYTES, 0
>  irq_stack_top:
> -         .space 4, 0
> +         .space 8, 0
> 
>  fiq_stack:
>          .space EXCEPTION_MODE_STACK_BYTES, 0
>  fiq_stack_top:
> -         .space 4, 0
> +         .space 8, 0
> 
>  undef_stack:
>          .space EXCEPTION_MODE_STACK_BYTES, 0
>  undef_stack_top:
> -        .space 4, 0
> +        .space 8, 0
> 
>  svc_stack:
>          .space EXCEPTION_MODE_STACK_BYTES, 0
>  svc_stack_top:
> -        .space 4, 0
> +        .space 8, 0
> 
>          //
>          // System mode stack
> 
> 
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-- 
Kornilios Kourtis